B11-P-04Limit of Detection for Dopant in Si Using Large Solid Angle Silicon Drift Detector

Abstract

Sensitivity of compositional analysis with energy dispersive X-ray spectrometer (EDS) has been improved, since a large solid angle Si drift detector (SDD) and a system with multiple detectors were realized [ 1 , 2 ]. Up to now, transmission electron microscopy (TEM)-EDS has been mostly untouched in the analysis of semiconductor dopants, because of their low concentration. There has been a strong desire to see “limit of detection (LOD)”, using a multiple SDD analysis system. In this study, we explore a concentration at LOD for a dopant in Si device using an FETEM (JEM-2800, JEOL) with two SDDs, whose sensing area is 100 mm 2 each. We examined an As-doped Si wafer as a sample. The concentration profile along z direction has been verified by secondary ion mass spectrometry (SIMS). We made a cross sectional sample for TEM observation. We define an dopant concentration ( C dopant ) at LOD as !!...!! where the I net is a net count of Si-K, the P/B is a ratio of a net count of Si (P) to the background count at an energy of the dopant element line (B), and k is the K factor for the line of a dopant[ 3 ]. The C dopant are calculated to be 30 ppm for As-K and 70 ppm for As-L using the eq. ( 1 ). The experimental concentration profiles were extracted using a quantitative analysis system (Thermo Fisher). The expected LODs by eq. ( 1 ) agree well with the experimental results.